With the increasing of the multi-media devices, touch screens have drawn more and more concern. The touch screen, as the newest input device, has advantages of rugged design, durability, fast response, space saving, easy communication, etc. Using such techniques, a user can realize operation on the host by gently touching the display screen with a finger, so that man-machine interaction become more direct, which brings great convenience for people who are unfamiliar with computer operations.
According to the technical principles, the touch screen can be classified into the following basic types: pressure-sensitive touch screen, resistive touch screen, capacitive touch screen, surface acoustic wave touch screen, and photosensitive touch screen.
The photosensitive touch screen generally includes a light sensor capable of detecting environment light. When a user touches a certain area using a finger or a writing tool such as pen, the detected result of the amount of light in the touch area obtained by using a light sensing needle corresponding to the touch area may vary due to blocking of the fingers. A processor in turn determines the area touched according to variation of the detected result of the amount of light detected by the light sensor (i.e., the light sensing needle), and then outputs positioning result. A hand is not necessary for controlling the photosensitive touch screen, and the writing tool such as pen and so on is also sufficient for operation even when operated with a glove.
However, it has been found in research that, when the environment light is weak, variation of the detected result of the amount of light obtained by the light sensor before and after the touch is not significant, and a detector cannot detect the touch position even if the user has touched the screen.
In view of this, it is necessary to improve the existing photosensitive touch screen, so as to improve sensitivity of the photosensitive touch screen.